1. Field of the Invention
The present invention relates to a color display device using projection lenses such as a projection television device.
2. Prior Art
In a so-called projection television device wherein images on the fluorescent faces of cathode-ray tubes of blue, red and green are projected onto a screen through projection lenses, its focusing performance has recently made a remarkable advancement, and the requirements for the performance of projection lenses which are key devices are becoming more and more strict every year. Under the circumstances, various lenses have been made public according to the fineness of image. Even under the same design idea, various lenses of different numbers of constituent lenses and different shapes of lens faces have been designed. For example, projection lenses of this type are disclosed in Japanese Patent Laid-Open No. 10642787. In the conventional projection lenses referred to above, there has been attained a high focusing performance after appropriate aberration correction for light of designed wavelength. In many cases, e ray (546.7 nm) of a wavelength close to the main wavelength of a green phosphor is used as a designed central wavelength. In the prior art, since projection lenses designed for such green phosphor are used also for red and blue cathode-ray tubes, the design for red and blue projection is not optimal. Consequently, the reproduced color image is not the best image, either.